1. Field of the Invention
The present invention relates generally to a stimulating medical device and, more particularly, to multi-channel stimulation of a medical device.
2. Related Art
Delivery of electrical stimulation to appropriate locations within a recipient or patient (referred to herein as a recipient) may be used for a variety of purposes. For example, function electrical stimulation (FES) systems may be used to deliver electrical pulses to certain muscles of a recipient to cause a controlled movement of a limb of the recipient.
As another example, a prosthetic hearing implant system may be used to directly deliver electrical stimulation to auditory nerve fibers of a recipient's cochlea to cause the recipient's brain to perceive a hearing sensation resembling the natural hearing sensation normally delivered to the auditory nerve.
Prosthetic hearing implant systems typically have two primary components: an external component commonly referred to as a speech processor, and an implanted component commonly referred to as a receiver/stimulator unit. Traditionally, both of these components cooperate with each other to provide sound sensations to a recipient.
The external component traditionally includes a microphone that detects sounds, such as speech and environmental sounds, a speech processor that selects and converts certain detected sounds, particularly speech, into a coded signal, a power source such as a battery, and an external transmitter antenna.
The coded signal output by the speech processor is transmitted transcutaneously to the implanted receiver/stimulator unit, commonly located within a recess of the temporal bone of the recipient. This transcutaneous transmission occurs via the external transmitter antenna which is positioned to communicate with an implanted receiver antenna disposed within the receiver/stimulator unit. This communication transmits the coded sound signal while also providing power to the implanted receiver/stimulator unit. Conventionally, this link has been in the form of a radio frequency (RF) link, but other communication and power links have been proposed and implemented with varying degrees of success.
The implanted receiver/stimulator unit traditionally includes the noted receiver antenna that receives the coded signal and power from the external component. The implanted unit also includes a stimulator that processes the coded signal and outputs an electrical stimulation signal to an intra-cochlea electrode assembly mounted to a carrier member. The electrode assembly typically has a plurality of electrodes that apply the electrical stimulation directly to the auditory nerve to produce a hearing sensation corresponding to the original detected sound.
In the conversion of sound to electrical stimulation by the speech processor, it is common in the prosthetic hearing implant field to allocate frequencies from a filter bank or similar frequency analyzer to individual electrodes of the electrode assembly. This “mapping” is typically done on a one-to-one basis, that is, each filter output is allocated to a single electrode. It is typical to allocate frequencies to electrodes that lie in positions in the cochlea that are close to the region that would naturally be stimulated in normal hearing. However, signal processing techniques implemented in conventional prosthetic hearing devices often fail to map to the optimal electrodes in the cochlea, thus limiting their ability to provide the desired perception of hearing.